Altered Condensed-Phase Electron Affinities of Carbonyl- 13C-, 14C-, and 17O-Substituted Ketones

Article abstract of DOI:10.1021/j100323a070

Electron spin resonance experiments have shown that the solution electron affinities of both benzoquinone (BQ) and benzophenone (BZO) in liquid ammonia are diminished when a 13C replaces the 12C in the carbonyl position.For the reaction ^*R+R^.-=^*R^.-+R, where ^*R represents the 13C-substituted material (either BZO-13C or BQ-13C), the equilibrium constants (K_eq) are 0.80 and 0.50 at -75 deg C for the BQ and BZO systems, respectively.The reduction of radioactive samples of benzophenone (mixtures of BZO and BZO-14C, 14C substitution at the carbonyl carbon) with deficient amounts of sodium metal in liquid ammonia followed by removal of the ammonia leaves a solid mixture of benzophenone and benzophenone ketyl.Sublimation of the neutral benzophenone from the anion radical salt produces benzophenone that is enhanced in radioactivity relative to the starting BZO/BZO-14C mixture.This enhancement in radioactivity is consistent with the equilibrium constant again being less than unity when ^*R represents the 14C-substituted benzophenone.In contrast to these results, substitution of the oxygen atom with 17O results in an increase in the relative solution electron affinity.This is explained in terms of the increase in "bonding" involving the oxygen upon reduction, due to ion association.